Parkinson's disease is a neurodegenerative disorder that is pathologically characterized by the presence of intracytoplasmic Lewy bodies (Lewy in Handbuch der Neurologie, M. Lewandowsld, ed., Springer, Berlin, pp. 920-933, 1912; Pollanen et al., J. Neuropath. Exp. Neurol. 52:183-191, 1993), the major components of which are filaments consisting of α-synuclein (Spillantini et al., Proc. Natl. Acad. Sci. USA 95:6469-6473, 1998; Arai et al., Neurosci. Lett. 259:83-86, 1999), an 140-amino acid protein (Ueda et al., Proc. Natl. Acad. Sci. USA 90:11282-11286, 1993). Two dominant mutations in α-synuclein causing familial early onset Parlinson's disease have been described suggesting that Lewy bodies contribute mechanistically to the degeneration of neurons in Parkinson's disease and related disorders (Polymeropoulos et al., Science 276:2045-2047, 1997; Kruger et al., Nature Genet. 18:106-108, 1998; Zarranz et al., Ann. Neurol. 55:164-173, 2004). Triplication and duplication mutation of the α-synuclein gene have been linked to early-onset of Parkinson's disease (Singleton et al., Science 302:841, 2003; Chartier-Harlin at al. Lancet 364:1167-1169, 2004; Ibanez et al., Lancet 364:1169-1171, 2004). In vitro studies have demonstrated that recombinant α-synuclein can indeed form Lewy body-like fibrils (Conway et al., Nature Med. 4:1318-1320, 1998; Hashimoto et al., Brain Res. 799:301-306, 1998; Nahri et al., J. Biol. Chem. 274:9843-9846, 1999). Both Parkinson's disease-linked α-synuclein mutations accelerate this aggregation process, demonstrating that such in vitro studies may have relevance for Parkinson's disease pathogenesis. Alpha-synuclein aggregation and fibril formation fulfills of the criteria of a nucleation-dependent polymerization process (Wood et al., J. Biol. Chem. 274:19509-19512, 1999). In this regard α-synuclein fibril formation resembles that of Alzheimer's β-amyloid protein (Aβ) fibrils. Alpha-synuclein recombinant protein, and non-Aβ component (known as NAC), which is a 35-amino acid peptide fragment of α-synuclein, both have the ability to form fibrils when incubated at 37° C., and are positive with amyloid stains such as Congo red (demonstrating a red/green birefringence when viewed under polarized light) and Thioflavin S (demonstrating positive fluorescence) (Hashimoto et al., Brain Res. 799:301-306, 1998; Ueda et al., Proc. Natl. Acad. Sci. USA 90:11282-11286, 1993).
Synucleins are a family of small, presynaptic neuronal proteins composed of α-, β-, and γ-synucleins, of which only α-synuclein aggregates have been associated with several neurological diseases (Ian et al., Clinical Neurosc. Res. 1:445-455, 2001; Trojanowski and Lee, Neurotoxicology 23:457-460, 2002). The role of synucleins (and in particular, alpha-synuclein) in the etiology of a number of neurodegenerative and/or amyloid diseases has developed from several observations. Pathologically, α-synuclein was identified as a major component of Lewy bodies, the hallmark inclusions of Parkinson's disease, and a fragment thereof was isolated from amyloid plaques of a different neurological disease, Alzheimer's disease. Biochemically, recombinant α-synuclein was shown to form amyloid-like fibrils that recapitulated the ultrastructural features of alpha-synuclein isolated from patients with dementia with Lewy bodies, Parlinson's disease and multiple system atrophy. Additionally, the identification of mutations within the α-synuclein gene, albeit in rare cases of familial Parkinson's disease, demonstrated an unequivocal link between synuclein pathology and neurodegenerative diseases. The common involvement of α-synuclein in a spectrum of diseases such as Parkinson's disease, dementia with Lewy bodies, multiple system atrophy and the Lewy body variant of Alzheimer's disease has led to the classification of these diseases under the umbrella term of “synucleinopathies.”
Fibrillization and aggregation of α-synuclein is thought to play major role in neuronal dysfunction and death of dopaminergic neurons in PD. Mutations in α-synuclein or genomic triplication of wild type α-synuclein (leading to its overexpression) cause certain rare familial forms of Parkinson's disease. In vitro and in vivo models suggest that over-expression of wild-type α-synuclein induces neuronal cell death. See, e.g., Polymeropoulos, et al. (1997) Science 276(5321):2045-7, Kruger, et al. (1998) Nat. Genet. 18(2):106-8, Singleton, et al. (2003) Science 302(5646):841, Miller, et al. (2004) Neurology 62(10):1835-8, Hashimoto, et al. (2003) Ann NY Acad Sci. 991:171-88, Lo Bianco, et al. (2002) Proc Natl Acad Sci USA. 99(16):10813-8, Lee, et al. (2002) Proc Natl Acad Sci USA. 99(13):8968-73, Masliah, et al. (2000) Science 287(5456):1265-9, Auluck, et al. (2002) Science 295(5556):865-8, Oluwatosin-Chigbu et al. (2003) Biochem Biophys Res Commun 309(3): 679-84, Klucken et al. (2004) J Biol. Chem. 279(24):25497-502. Protecting neurons from the toxic effects of α-synuclein is a promising strategy for treating Parkinson's disease and other synucleinopathies such as Lewy body dementia.
Thus, there is a need for compounds and compositions that prevent α-synuclein toxicity and/or aggregation and/or promote α-synuclein fibril disaggregation. Such compounds and composition are useful in treating or ameliorating one or more symptoms of α-synuclein mediated diseases and disorders, or diseases and disorders in which a-synuclein fibril formation is implicated, including but not limited to, Parkinson's disease, dementia with Lewy bodies, multiple system atrophy and the Lewy body variant of Alzheimer's disease.